/*
 * COPYRIGHT (C) 2017-2019, zhllxt
 *
 * author   : zhllxt
 * email    : 37792738@qq.com
 * 
 * refrenced from https://github.com/fffaraz/cppDES
 */

#ifndef __DES_HPP__
#define __DES_HPP__

#include <cassert>
#include <cstdint>
#include <cstring>
#include <string>
#include <sstream>

class des
{
public:
	des(uint64_t key)
	{
		keygen(key);
	}
	/*
	 * key.size() should be 8,if less than 8,key will be padded with '\0',if greater than 8,key will be truncate to 8
	 */
	des(std::string key)
	{
		uint64_t k = 0;
		key.resize(sizeof(k));
		std::memcpy((void *)&k, (const void *)key.data(), sizeof(k));
		keygen(k);
	}
	~des()
	{
	}

	des(const des & other)
	{
		std::memcpy((void *)(this->sub_key), (const void *)(other.sub_key), sizeof(this->sub_key));
	}

	des & operator=(const des & other)
	{
		std::memcpy((void *)(this->sub_key), (const void *)(other.sub_key), sizeof(this->sub_key));
		return (*this);
	}

	uint64_t encrypt(uint64_t block)
	{
		return do_des(block, false);
	}
	uint64_t decrypt(uint64_t block)
	{
		return do_des(block, true);
	}

	/*
	 * note : if msg contains '\0',there may be a wrong result when decrypt
	 */
	std::string encrypt(const std::string & msg)
	{
		std::istringstream iss(msg);
		std::ostringstream oss;

		uint64_t buffer = uint64_t(0);

		while (iss.read((char*)&buffer, 8))
		{
			buffer = encrypt(buffer);

			oss.write((const char *)&buffer, 8);

			buffer = uint64_t(0);
		}

		if (iss.gcount() > std::streamsize(0))
		{
			// Amount of padding needed
			uint8_t padding = uint8_t(8 - iss.gcount());

			// Pad block with a 1 followed by 0s
			uint8_t shift = static_cast<uint8_t>(padding * uint8_t(8));
			buffer <<= shift;
			//buffer |= uint64_t(0x0000000000000001) << (shift - uint8_t(1));

			buffer = encrypt(buffer);

			oss.write((const char *)&buffer, 8);
		}

		return oss.str();
	}
	std::string decrypt(const std::string & msg)
	{
		if (msg.empty())
			return std::string();

		if((msg.size() % 8) != 0)
			return std::string();

		std::istringstream iss(msg);
		std::ostringstream oss;

		iss.seekg(0, std::ios::end);
		std::streampos size = iss.tellg();
		iss.seekg(0, std::ios::beg);

		uint64_t block = (size / 8) - 1;

		uint64_t buffer = uint64_t(0);

		for (uint64_t i = 0; i < block; ++i)
		{
			iss.read((char*)&buffer, 8);

			buffer = decrypt(buffer);

			oss.write((const char *)&buffer, 8);

			buffer = uint64_t(0);
		}

		{
			// Read last line of file
			iss.read((char*)&buffer, 8);

			buffer = decrypt(buffer);

			// Amount of padding on file
			uint8_t padding = uint8_t(0);

			// Check for and record padding on end
			while (!(buffer & uint64_t(0x00000000000000ff)))
			{
				buffer >>= 8;
				++padding;
			}

			oss.write((const char *)&buffer, 8 - padding);
		}

		return oss.str();
	}

protected:
	uint64_t do_des(uint64_t block, bool mode)
	{
		// applying initial permutation
		block = ip(block);

		// dividing T' into two 32-bit parts
		uint32_t L = static_cast<uint32_t>((block >> 32) & L64_MASK);
		uint32_t R = static_cast<uint32_t>(block & L64_MASK);

		// 16 rounds
		for (uint8_t i = 0; i < 16; ++i)
		{
			uint32_t F = mode ? f(R, sub_key[15 - i]) : f(R, sub_key[i]);
			feistel(L, R, F);
		}

		// swapping the two parts
		block = (((uint64_t)R) << 32) | (uint64_t)L;
		// applying final permutation
		return fp(block);
	}
	void keygen(uint64_t key)
	{
		// initial key schedule calculation
		uint64_t permuted_choice_1 = 0; // 56 bits
		for (uint8_t i = 0; i < 56; ++i)
		{
			permuted_choice_1 <<= 1;
			permuted_choice_1 |= (key >> (64 - PC1[i])) & LB64_MASK;
		}

		// 28 bits
		uint32_t C = (uint32_t)((permuted_choice_1 >> 28) & 0x000000000fffffff);
		uint32_t D = (uint32_t)(permuted_choice_1 & 0x000000000fffffff);

		// Calculation of the 16 keys
		for (uint8_t i = 0; i < 16; ++i)
		{
			// key schedule, shifting Ci and Di
			for (uint8_t j = 0; j < ITERATION_SHIFT[i]; ++j)
			{
				C = (0x0fffffff & (C << 1)) | (0x00000001 & (C >> 27));
				D = (0x0fffffff & (D << 1)) | (0x00000001 & (D >> 27));
			}

			uint64_t permuted_choice_2 = (((uint64_t)C) << 28) | (uint64_t)D;

			sub_key[i] = 0; // 48 bits (2*24)
			for (uint8_t j = 0; j < 48; ++j)
			{
				sub_key[i] <<= 1;
				sub_key[i] |= (permuted_choice_2 >> (56 - PC2[j])) & LB64_MASK;
			}
		}
	}

	uint64_t ip(uint64_t block)
	{
		// initial permutation
		uint64_t result = 0;
		for (uint8_t i = 0; i < 64; ++i)
		{
			result <<= 1;
			result |= (block >> (64 - IP[i])) & LB64_MASK;
		}
		return result;
	}
	uint64_t fp(uint64_t block)
	{
		// inverse initial permutation
		uint64_t result = 0;
		for (uint8_t i = 0; i < 64; ++i)
		{
			result <<= 1;
			result |= (block >> (64 - FP[i])) & LB64_MASK;
		}
		return result;
	}

	void feistel(uint32_t &L, uint32_t &R, uint32_t F)
	{
		uint32_t temp = R;
		R = L ^ F;
		L = temp;
	}
	uint32_t f(uint32_t R, uint64_t k) // f(R,k) function
	{
		// applying expansion permutation and returning 48-bit data
		uint64_t s_input = 0;
		for (uint8_t i = 0; i < 48; ++i)
		{
			s_input <<= 1;
			s_input |= (uint64_t)((R >> (32 - EXPANSION[i])) & LB32_MASK);
		}

		// XORing expanded Ri with Ki, the round key
		s_input = s_input ^ k;

		// applying S-Boxes function and returning 32-bit data
		uint32_t s_output = 0;
		for (uint8_t i = 0; i < 8; ++i)
		{
			// Outer bits
			char row = static_cast<char>((s_input & (0x0000840000000000 >> 6 * i)) >> (42 - 6 * i));
			row = static_cast<char>((row >> 4) | (row & 0x01));

			// Middle 4 bits of input
			char column = (char)((s_input & (0x0000780000000000 >> 6 * i)) >> (43 - 6 * i));

			s_output <<= 4;
			s_output |= (uint32_t)(SBOX[i][16 * row + column] & 0x0f);
		}

		// applying the round permutation
		uint32_t f_result = 0;
		for (uint8_t i = 0; i < 32; ++i)
		{
			f_result <<= 1;
			f_result |= (s_output >> (32 - PBOX[i])) & LB32_MASK;
		}

		return f_result;
	}

private:
	uint64_t sub_key[16] = { 0 }; // 48 bits each

	// Permuted Choice 1 Table [7*8]
	const char PC1[7 * 8] =
	{
		57, 49, 41, 33, 25, 17,  9,
		1, 58, 50, 42, 34, 26, 18,
		10,  2, 59, 51, 43, 35, 27,
		19, 11,  3, 60, 52, 44, 36,

		63, 55, 47, 39, 31, 23, 15,
		7, 62, 54, 46, 38, 30, 22,
		14,  6, 61, 53, 45, 37, 29,
		21, 13,  5, 28, 20, 12,  4
	};

	// Permuted Choice 2 Table [6*8]
	const char PC2[6 * 8] =
	{
		14, 17, 11, 24,  1,  5,
		3, 28, 15,  6, 21, 10,
		23, 19, 12,  4, 26,  8,
		16,  7, 27, 20, 13,  2,
		41, 52, 31, 37, 47, 55,
		30, 40, 51, 45, 33, 48,
		44, 49, 39, 56, 34, 53,
		46, 42, 50, 36, 29, 32
	};

	// Iteration Shift Array
	const char ITERATION_SHIFT[16] =
	{
		//  1   2   3   4   5   6   7   8   9  10  11  12  13  14  15  16
		1,  1,  2,  2,  2,  2,  2,  2,  1,  2,  2,  2,  2,  2,  2,  1
	};

	const uint32_t LB32_MASK = 0x00000001;
	const uint64_t LB64_MASK = 0x0000000000000001;
	const uint64_t L64_MASK  = 0x00000000ffffffff;

	// Initial Permutation Table [8*8]
	const char IP[8 * 8] =
	{
		58, 50, 42, 34, 26, 18, 10, 2,
		60, 52, 44, 36, 28, 20, 12, 4,
		62, 54, 46, 38, 30, 22, 14, 6,
		64, 56, 48, 40, 32, 24, 16, 8,
		57, 49, 41, 33, 25, 17,  9, 1,
		59, 51, 43, 35, 27, 19, 11, 3,
		61, 53, 45, 37, 29, 21, 13, 5,
		63, 55, 47, 39, 31, 23, 15, 7
	};

	// Inverse Initial Permutation Table [8*8]
	const char FP[8 * 8] =
	{
		40, 8, 48, 16, 56, 24, 64, 32,
		39, 7, 47, 15, 55, 23, 63, 31,
		38, 6, 46, 14, 54, 22, 62, 30,
		37, 5, 45, 13, 53, 21, 61, 29,
		36, 4, 44, 12, 52, 20, 60, 28,
		35, 3, 43, 11, 51, 19, 59, 27,
		34, 2, 42, 10, 50, 18, 58, 26,
		33, 1, 41,  9, 49, 17, 57, 25
	};

	// Expansion table [6*8]
	const char EXPANSION[6 * 8] =
	{
		32,  1,  2,  3,  4,  5,
		4,  5,  6,  7,  8,  9,
		8,  9, 10, 11, 12, 13,
		12, 13, 14, 15, 16, 17,
		16, 17, 18, 19, 20, 21,
		20, 21, 22, 23, 24, 25,
		24, 25, 26, 27, 28, 29,
		28, 29, 30, 31, 32,  1
	};

	// The S-Box tables [8*16*4]
	const char SBOX[8][64] =
	{
		{
			// S1
			14,  4, 13,  1,  2, 15, 11,  8,  3, 10,  6, 12,  5,  9,  0,  7,
			0, 15,  7,  4, 14,  2, 13,  1, 10,  6, 12, 11,  9,  5,  3,  8,
			4,  1, 14,  8, 13,  6,  2, 11, 15, 12,  9,  7,  3, 10,  5,  0,
			15, 12,  8,  2,  4,  9,  1,  7,  5, 11,  3, 14, 10,  0,  6, 13
		},
		{
			// S2
			15,  1,  8, 14,  6, 11,  3,  4,  9,  7,  2, 13, 12,  0,  5, 10,
			3, 13,  4,  7, 15,  2,  8, 14, 12,  0,  1, 10,  6,  9, 11,  5,
			0, 14,  7, 11, 10,  4, 13,  1,  5,  8, 12,  6,  9,  3,  2, 15,
			13,  8, 10,  1,  3, 15,  4,  2, 11,  6,  7, 12,  0,  5, 14,  9
		},
		{
			// S3
			10,  0,  9, 14,  6,  3, 15,  5,  1, 13, 12,  7, 11,  4,  2,  8,
			13,  7,  0,  9,  3,  4,  6, 10,  2,  8,  5, 14, 12, 11, 15,  1,
			13,  6,  4,  9,  8, 15,  3,  0, 11,  1,  2, 12,  5, 10, 14,  7,
			1, 10, 13,  0,  6,  9,  8,  7,  4, 15, 14,  3, 11,  5,  2, 12
		},
		{
			// S4
			7, 13, 14,  3,  0,  6,  9, 10,  1,  2,  8,  5, 11, 12,  4, 15,
			13,  8, 11,  5,  6, 15,  0,  3,  4,  7,  2, 12,  1, 10, 14,  9,
			10,  6,  9,  0, 12, 11,  7, 13, 15,  1,  3, 14,  5,  2,  8,  4,
			3, 15,  0,  6, 10,  1, 13,  8,  9,  4,  5, 11, 12,  7,  2, 14
		},
		{
			// S5
			2, 12,  4,  1,  7, 10, 11,  6,  8,  5,  3, 15, 13,  0, 14,  9,
			14, 11,  2, 12,  4,  7, 13,  1,  5,  0, 15, 10,  3,  9,  8,  6,
			4,  2,  1, 11, 10, 13,  7,  8, 15,  9, 12,  5,  6,  3,  0, 14,
			11,  8, 12,  7,  1, 14,  2, 13,  6, 15,  0,  9, 10,  4,  5,  3
		},
		{
			// S6
			12,  1, 10, 15,  9,  2,  6,  8,  0, 13,  3,  4, 14,  7,  5, 11,
			10, 15,  4,  2,  7, 12,  9,  5,  6,  1, 13, 14,  0, 11,  3,  8,
			9, 14, 15,  5,  2,  8, 12,  3,  7,  0,  4, 10,  1, 13, 11,  6,
			4,  3,  2, 12,  9,  5, 15, 10, 11, 14,  1,  7,  6,  0,  8, 13
		},
		{
			// S7
			4, 11,  2, 14, 15,  0,  8, 13,  3, 12,  9,  7,  5, 10,  6,  1,
			13,  0, 11,  7,  4,  9,  1, 10, 14,  3,  5, 12,  2, 15,  8,  6,
			1,  4, 11, 13, 12,  3,  7, 14, 10, 15,  6,  8,  0,  5,  9,  2,
			6, 11, 13,  8,  1,  4, 10,  7,  9,  5,  0, 15, 14,  2,  3, 12
		},
		{
			// S8
			13,  2,  8,  4,  6, 15, 11,  1, 10,  9,  3, 14,  5,  0, 12,  7,
			1, 15, 13,  8, 10,  3,  7,  4, 12,  5,  6, 11,  0, 14,  9,  2,
			7, 11,  4,  1,  9, 12, 14,  2,  0,  6, 10, 13, 15,  3,  5,  8,
			2,  1, 14,  7,  4, 10,  8, 13, 15, 12,  9,  0,  3,  5,  6, 11
		}
	};

	// Post S-Box permutation [4*8]
	const char PBOX[4 * 8] =
	{
		16,  7, 20, 21,
		29, 12, 28, 17,
		1, 15, 23, 26,
		5, 18, 31, 10,
		2,  8, 24, 14,
		32, 27,  3,  9,
		19, 13, 30,  6,
		22, 11,  4, 25
	};

};

#endif // !__DES_HPP__
